Central Coast Mariners Friday suffered a double blow to their Australian A-League title defence with the transfers of defender Trent Sainsbury and veteran striker Daniel McBreen to overseas clubs.

Sainsbury, one of the league's leading defenders, has signed a two and a half season deal with Dutch club PEC Zwolle, while 36-year-old McBreen was granted a transfer back to China, the Mariners said.

The Mariners had initially blocked McBreen's bid to move back to Asia but announced late Friday that he would re-join Chinese Super League outfit Shanghai SPIG on a one-season deal.

The 22-year-old Sainsbury, an aspiring Socceroo, said he was excited to further his career in the Eredivisie, one of Europe's top leagues.

"The Dutch first division is big and now I have to go there and give it my all," Sainsbury said.